Thermal Test And Numerical Simulation Research On Energy Storage Pile

During the period of the Twelfth Five-year Plan, the work for saving energy and reducingemission will get into a hard time. China has been the biggest country in energy and resourceconsuming. Its architectural energy consuming occupies30percent of the total energyconsumption, having been the field that increases the most rapidly in energy and resourceconsumption, especially northern architectural consumption occupies over40percent of that inurban and rural areas nationwide and shows a trend of gradual increase. However, the structure ofenergy and resource mainly relies on coal and carbon as well as other fossil fuels. Theenvironmental pollution caused by the smog and CO2out of burning coal and carbon has gothighly worldwide attention. Therefore, the development and utilization of clean energy has beenan urgent necessity.Simultaneously, the GSHPs (ground-source heat pump systems) have become a major formof clean energy by means of their advantages such as saving energy and reducing emission, theirweaknesses are especially obvious, though. Firstly, the GSHPs need lay underground heatexchange tubes, which need consider underground well drillings, whose cost will be a little higher.The deeper the heat exchange tube is laid, the higher the total cost will be. Secondly, drilling awell has to be related to the geological conditions. For instance, if heat exchange wells are drilledon the rock layers, the cost of drilling wells will be1/3that of the total heat exchange system. If itis drilled on an especially complex layer, its cost will be half that of the total, both of which will toa big extent increase the project cost of GSHPs. At last, it will take a long period of time toconfirm the well drilling process of GSHPs before building a pile foundation. On the contrary, ifthe needed time is shortened, it will lead to an adverse impact on both construction and outerpipeline process.To sum up, this paper presents that the technology of energy pile can simplify the process ofthe heat exchange well in GSHPs. The technology of storing heat in energy piles is to turn theconcrete pile laid underground into a part of GSHPs. The heat exchange tube is to be laid in thepile, regarding the pile as the heat exchange well and burying the heat exchange tube into the pile.The energy pile can transmit heat with the earth around by means of the link between collectorpipe and heat pump, through which the part of drilling wells in GSHPs as well as the grouting and back filling of the heat exchange well can be cut down. This technology can reduce the projectcost and shorten the construction period to save the land. It also gives a new form of heating thatcan effectively reduce the heating fees and decrease the impact of environmental pollution byburning coal. If it gets a wide promotion, there will be a handsome profit and social effect.This paper is to do some researches according to aspects as follows:First, as a result of laying the heat exchange tubes in concrete piles, the bearing capacity ofthe piles is broken and hence the safety of buildings is influenced. Thus, the structural stability andthe situation of heat transmitting of concrete piles should be taken into consideration. Choose thematerial of piles and do experiments and researches on the proportion of the material of energypiles by the orthogonal method. Make the experimental sites after the best proportion for energypiles is got, and do a test about compressive resisting and static load as well as a separation test tocheck the concrete mix proportion of the energy pile. The test shows that as a strengtheningmaterial, steel fiber is accessible for piles of storing heat to load strengthening. And under thecondition of a reasonable proportion, the strengthened piles can meet the origin designing demandabsolutely. As a gelatinized material for the energy piles, either normal or compound silicatecement is accessible. The experiments verify that as the gelatinized material, compound silicatecement can meet all demands of concrete piles better. Industrial graphite and scrap copper canwell improve the heat-conducting property. Meanwhile, they can cut down the mechanicalproperty. So they have to be controlled in a certain extent and cannot be added too much toincrease heat-transmitting index of piles.Second, create physical and mathematics models of energy piles and use the software Fluentto simulate the temperature field. And we get the result that energy piles has the best effect whosediameter is300mm and separation distance between the exit and entrance of heat exchange tubesis120mm. At the time of the single-pile simulation, the heat-effect radius can reach1.5meters. Inthe process of continuous heat-storing of energy piles, the soil temperature around the pilesincreases. The effective scope reflects round and jujube-pit distribution respectively when seenlaterally and longitudinally.In addition, on the basis of researches on the proportion of concrete material, an experimentalstage of heat storing in energy piles is established to study the changes of the inner and outer pilesas well as the temperature field in the process of storing heat. Meanwhile, it also studies the regulation of heat transmitting. Through the heat storing experiment in single energy pile, theresult shows that the experimental data when buried0.65meters deep gains a smaller externaldisturbance and provides a better reference value for simulation study the process of saving heat inunderground energy piles. The range of temperature at the exit and entrance of piles can reach1℃at the beginning of saving heat, while that of heat exchange system in single-U tubes with thelength of12meters can reach10℃.Finally, do comparative analysis between simulation results and experimental results andanalyze temperature changing regulations of the inner and outer piles and soil in the process ofstoring heat to confirm a reasonable heat saving model.